Load Balancing and Session Persistence in Packet Networks

ABSTRACT

Methods and systems for performing load balancing and session persistence in IP (e.g., IPv6) networks are described herein. Some aspects relate to a destination options extension header that may be defined as a load balancing session persistence option (LBSPO) for storing a client identifier and a server identifier for each of a client and a server during a session. Packets sent between the client and the server may include the LBSPO with the client and server identifiers. A load balancer with a virtual IP address of a target application can perform session persistence and assign a destination server to a client based on a preexisting session between the server and the client, as determined by the LBSPO information. While a target VIP node may process data packets based on the LBSPO information, once established, the LBSPO information may remain unchanged for the duration of the session.

FIELD

Aspects described herein relate generally to packet data networks. Someaspects relate to session persistence and load balancing in IP networks.

BACKGROUND

In packet switched networks such as the Internet, there is presently noefficient way to maintain session persistence when a session transformsfrom an unsecured session (e.g., HTTP) to a secure session (e.g.,HTTPS). In architectures using megaproxies (e.g., redirecting users tocached versions of web sites, or for control, surveillance and datamining purpose, as is sometimes done by ISPs and enterprises), the useof cookie switching or URL switching in a load balancer (LB) aresometimes used.

In web applications, a LB may use a URL or cookie in a HTTP request toselect an appropriate server. However, in order to examine theapplication packets, the LB must postpone the binding of a TCPconnection to a server until after the application request is received.This is known as “delayed binding”. In a delayed binding scenario, theLB completes the TCP connection setup with the client on behalf of theserver. Once the HTTP request is received, the LB selects the server,establishes a connection with the server, and forwards the HTTP request.The LB must translate the sequence number of all reply packets from theserver to match what the LB used on the client-side connection. The LBmust also change the ACK sequence number for packets from client to theserver. Delayed Binding therefore impacts the performance of the LBbecause of the need for sequence number translation, and delayed bindingcan also increase the response time of a user's request to anapplication running on a server.

In shopping-cart applications, the LB typically must associate the firstHTTPS connection request from a client with an earlier HTTP requestreceived from the client. Source IP-based persistence does not work wellwhen dealing with a mega proxy server, because when a user transitionsfrom HTTP to HTTPS, the LB can no longer read the cookie because thecookie is encrypted.

Current practices for HTTP to HTTPS transition include the use of ashared back-end storage or database system. When the SSL (or TLS)session is initiated, the SSL server obtains the shopping-cartinformation from the back-end database and then processes it. However,this solution requires the server with the shopping cart to write theinformation to a back-end database. Another known option is to usemiddleware software to make all the servers appear as one big virtualserver to the client application. A cookie is used to track the useridentification. Once the application receives the first HTTPS request,the application uses the cookie to retrieve the data structure thatcontains the correct context.

In another known solution, a LB may be configured to bind a differentport number on the virtual IP address (VIP) to port 443 of a differentreal server. When the real server generates the Web page reply thatcontains the checkout button, the LB links its own port number to thatbutton (e.g., by generating a hyperlink for the checkout button).

In another known solution using an SSL accelerator, the SSL accelerationproduct terminates secure connections and converts the HTTPS request toan HTTP request. The LB redirects requests received on port 443 to theSSL accelerator, and maintains session persistence via a cookie or othermethod that is no longer encrypted.

Each of these known solutions consumes resources and overhead within aLB, thereby reducing the number of sessions and/or the amount of trafficthe LB could otherwise handle.

BRIEF SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects described herein. This summary is not anextensive overview. It is not intended to identify key or criticalelements of the disclosure or to delineate the scope of the disclosure.The following summary merely presents some concepts directed totechniques for providing session persistence and load balancing inpacket networks, for example in IPv6 networks, in a simplified form as aprelude to the more detailed description provided below.

A first aspect is directed to a non-transitory computer readable mediumhaving a data structure stored thereon, where the data structure storesdata for a load balancing session persistence option. The data structuremay include an IP header, a destination options extension header (DOEH),and an IP payload. The DOEH may further include a first data fieldidentifying the DOEH as conforming to a predefined option usable withload balancing, a second data field identifying a length of a DOEHpayload field, and the DOEH payload field itself. The DOEH payload fieldmay be made up of third and fourth data fields, where the third datafield stores a client identifier, and the fourth data field stores aserver identifier.

According to another aspect, an apparatus may be specifically adapted orconfigured to manage and process IP data packets having a load balancingsession persistence option defined, e.g., in a destination optionsextension header. The apparatus may include a processor, and memorystoring computer executable instructions that, when executed by theprocessor, cause the apparatus to perform certain actions, includingreceiving an Internet Protocol (IP) data packet. The IP data packetincludes an IP header, a destination options extension header (DOEH),and an IP payload. The DOEH includes a first data field identifying theDOEH as conforming to a predefined option usable with load balancing andsession persistence, a second data field identifying a length of a DOEHpayload field, and the DOEH payload field itself. The DOEH payload fieldmay further include third and fourth data fields, where the third datafield stores a client identifier, and the fourth data field stores aserver identifier.

Yet another aspect is directed to a method for handling IP data packetsbased on load balancing and session persistence needs. The method mayinclude an intermediary node of an Internet Protocol (IP) data networkreceiving an IP data packet. The IP data packet may include an IPheader, a destination options extension header (DOEH), and an IPpayload. The DOEH includes a first data field identifying the DOEH asconforming to a predefined option usable with load balancing and sessionpersistence, a second data field identifying a length of a DOEH payloadfield, and the DOEH payload field itself. The DOEH payload field mayfurther include third and fourth data fields, where the third data fieldstores a client identifier, and the fourth data field stores a serveridentifier. The intermediary node may then process the IP data packetbased on the IP header without allowing modification to the DOEH, andthe intermediary node sending the IP data packet to either a next hopnode or a destination server, based on the processing of the datapacket.

Processing of the IP data packet based on the IP header may be performedwithout allowing modification to the DOEH header. Processing the IP datapacket may include forwarding the IP data packet to a next hop in a datanetwork, assigning a server to a session with the client based on theDOEH, or assigning a server to a session with the client based on loadbalancing when no server information is present in the DOEH. Processingthe data packet may further include associating an HTTPS packet with apreviously received HTTP packet based on information stored in the DOEH.

According to some aspects, each of the client and server identifiers maybe an address such as a network address. In one embodiment, the firstdata field is 8 bits storing a binary value of 1, the second data fieldis 8 bits storing a binary value of 4, the third data field is 128 bitsstoring an IPv6 address of the client, and wherein the fourth data fieldis 128 bits storing an IPv6 address of the server. According to someaspects, a value of the third data field, once established by a client,cannot be changed within a same session, and a value of the fourth datafield, once established by a server, also cannot be changed within thesame session.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the disclosure and the advantagesthereof may be acquired by referring to the following description inconsideration of the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates an example packet header according to IPv6.

FIG. 2 illustrates example extension headers available according toIPv6.

FIG. 3 illustrates example extension header chaining according to IPv6.

FIG. 4 illustrates an example extension header format according to IPv6.

FIG. 5 illustrates an example load balancing session persistence option(LBSPO) in an IPv6 destination options extension header according to oneor more aspects described herein.

FIG. 6 illustrates an example network architecture for maintainingsession persistence and performing load balancing according to one ormore aspects described herein.

FIG. 7 illustrates example IPv6 data packets using a LBSPO destinationoptions extension header as data packets initially progress from clientto server according to one or more aspects described herein.

FIG. 8 illustrates example IPv6 data packets using a LBSPO destinationoptions extension header as data packets initially progress from serverto client according to one or more aspects described herein.

FIG. 9 illustrates example IPv6 data packets using a LBSPO destinationoptions extension header as data packets subsequently progress fromclient to server according to one or more aspects described herein.

FIG. 10 illustrates example IPv6 data packets LBSPO destination optionsextension header as data packets subsequently progress from server toclient according to one or more aspects described herein.

FIG. 11 illustrates a method for performing session persistence and/orload balancing according to one or more aspects described herein.

FIG. 12 illustrates example load balancing information maintained by aload balancer node according to one or more aspects described herein.

DETAILED DESCRIPTION

In the following description of the various embodiments, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown by way of illustration various embodiments in which thedisclosure may be practiced. It is to be understood that otherembodiments may be utilized and structural and functional modificationsmay be made without departing from the scope of the disclosure. Also, itis to be understood that the phraseology and terminology used herein arefor the purpose of description and should not be regarded as limiting.Rather, the phrases and terms used herein are to be given their broadestinterpretation and meaning. The use of “including” and “comprising” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items and equivalents thereof.The use of the terms “mounted,” “connected,” “coupled,” “positioned,”“engaged” and similar terms, is meant to include both direct andindirect mounting, connecting, coupling, positioning and engaging.

Packet-switched data commonly traverses multiple networks, such asdifferent service operators' networks, between the origin anddestination of each packet. Network operators may include any thatmanages one or more distinct and/or contiguous physical networks, or aportion thereof, over which Internet Protocol traffic may be sent, e.g.,including but not limited to Internet multi-service operators, wirelessand mobile-to-mobile service operators, as well as other Internetservice providers. These operators may be referred to herein genericallyas an Internet Service Provider (ISP) or network operator (NO), andreference to one does not exclude the other. Many Networks operators arein the midst of upgrading resources to accommodate IPv6, defined by RFC2460, “Internet Protocol, Version 6 (Specification)” (“RFC 2460”). Asthis IPv6 data traverses networks between a client and a server, eachdata packet 101 (shown in FIG. 1) may pass through proxy servers andload balancers, each of which may further redirect the traffic alongdifferent paths to different nodes, and ultimately to different physicaland/or logical servers. A server may be any data processing or computingdevice capable of handling requests from one or more client devices.

By way of general introduction, the IPv6 header (versus the previousIPv4 header) was simplified to a fixed size of 40 bytes, and then anynumber of subsequent extension headers may be added. The IPv4 header hadmore fields and was 20 to 60 bytes in size. Additional IP options weremoved from the main IPv6 header into additional headers, referred to asextension headers (EH) that may be appended to the main header asneeded. The permissible EHs are shown in FIG. 2. With reference to FIG.3 and FIG. 4, the first 8 bits 403 of each EH 401 identify the nextheader (another EH or upper layer protocol, such as TCP) following thatheader. The next 8 bits 405 specify the length of the option data field,in octets, not including the first 8 octets. The option data field 407is a variable-length field, of length such that the complete DestinationOptions header is an integer multiple of 8 octets long, and contains oneor more type/tag, length, value (TLV) encoded options. Extension headersmay include a hop-by-hop header, destination header, routing header,fragment header, authentication header, and encapsulating securitypayload (ESP) header. Only the hop-by-hop header must be examined byevery node on a path and, if present, the hop-by-hop header must be thefirst header following the main IPv6 header. Every EH must only occuronce. Only the destination options extension header (DOEH) may occurtwice: once before a routing EH and again before the upper layer header(after the ESP header). Further information regarding extension headersis included in RFC 2460.

Some aspects described herein introduce and define an option for the usein an IPv6 destination options extension header to assist with loadbalancing and session persistence. According to aspects describedherein, the IPv6 destination options extension header may be used toeliminate the need for delayed binding to maintain session persistence,thereby increasing the performance of load balancers and speeding upapplication response time. The IPv6 destination options extension headeris not encrypted when placed before the ESP header, as is intendedherein. As a result, shopping-cart applications can carry forwardsession state information as a user transitions from unsecured (e.g.,HTTP) to secured (e.g., HTTPS) requests so that all connections of thesame session from a given user are sent to the same server for both HTTPand HTTPS traffic. The use of the destination options extension headeras described herein can thereby eliminate the need for the use of aback-end databases, middleware, and complicated configuration of theload balancer, to achieve session persistence. As a result, a loadbalancer can handle more connections, each with reduced latency, thanpreviously possible.

With reference to FIG. 5, a destination options extension header (DOEH)501 may be defined with a load balancing session persistence option(LBSPO). For brevity, a destination options extension header (DOEH)employing a load balancing session persistence option (LBSPO) asdescribed herein may be referred to as an LBSPO header. LBSPO header 501includes predefined fields 503, 505 according to RFC 2460. Namely, field503 corresponds to field 403 and defines the next header or protocol.Field 505 corresponds to field 405 and defines the length of the datapayload included with the header. Fields 507, 509, 511, and 513,collectively, correspond to field 407, and make up the payload portionof the LBSPO header 501. Field 507 specifies an option type or value. Inthe example illustrated in FIG. 5 the 1 octet option type 507 may have avalue of 1 (binary: 00000001) identifying the load balancing sessionpersistence option and thereby defining the extension header as an LBSPOheader. Other predefined values may alternatively be used, provided thateach device understands that value corresponds to the LBSPO header.Field 509 specifies the length of the option data. In the exampleillustrated in FIG. 5, the 1 octet option length 509 has a valueindicating the option data is 32 bytes (binary: 00000100). When thesession persistence option is used by a load balancer, the option data(or “value” within the TLV encoding) for the load balancing sessionpersistence option is split into two fields: client 511 and server 513.Client 511 (bits 17-144) may be used to store the IPv6 address of thesource application or client. For example, client 511 may be the same asthe 9^(th)-24^(th) bytes of the original IPv6 packet header). Server 513may be used to store the IPv6 address of the ultimate server ordestination machine to which the packet is sent. However, server 513might not get populated until that machine is known, as furtherdescribed below.

Using the LBSPO header shown in FIG. 5, a load balancer (LB) may use theclient 511 and other criteria to pick a server for load balancingpurposes. The server chosen by the LB can then respond with a LBSPOheader in its corresponding IPv6 response packet and indicate its ownIPv6 address in server field 513. Subsequent request and responsepackets should also include the LBSPO header with both the client 511and server 513 information unchanged. The LB may use the server 513 IPv6address for session persistence purposes. As indicated in RFC 2460, ifeither the authentication header or ESP header is present, the sessionpersistence information (in the destination options header) should beplaced before those headers, not after.

FIG. 6 illustrates a sample network architecture 600 that may benefitfrom use of the LBSPO header and other aspects described herein.Architecture 600 supports one or more client devices 601, 602, 603(e.g., user devices, such as computing devices, smart phones, displaydevices, etc.) communicating with one or more ultimate server devices631, 632, 633. However, the communications may pass through variousintermediaries, hops, nodes, networks, etc., while traversingarchitecture 600. For example, client data packets might initially getrouted to one or more proxy servers 611, 612, which then forward thecommunications to the server(s) via a wide area network 615, e.g., theInternet (other networks may of course be used). However, beforearriving at the server 631, 632, 633, data packets might be received bya load balancer 620. Load balancer 620 determines which particularserver or server instance should receive the data packet, and thenforwards the data packet to the appropriate server. In some embodimentsa pair of load balancers may be used in production networks forresiliency. The LBSPO header may be used in such a network setup.

In an IPv4 implementation of architecture 600, when a user opensmultiple connections, the connections can be distributed across multipleproxy servers. The proxy server that makes or sends the request to thedestination web site could be different for each connection. The loadbalancer (LB) at the destination web site identifies the IP address ofthe proxy server as the source IP address, because the proxy server willhave replaced the original sender address with its own. If the LBperforms session persistence based on the source IPv4 address,connections from the same user that are processed by different proxyservers may be sent to different application servers because the LB willview messages originating from different proxy servers as beingassociated with different users, thereby causing the applicationtransaction to break. In addition, the LB may direct all connectionsfrom a given proxy server to the same application server when a singleproxy server is sending communications on behalf of many differentclient machines, resulting in an improperly balanced traffic load. Tocorrect this problem, prior art IPv4 systems use delayed binding asdiscussed above, but delayed binding hurts LB performance in terms ofthe number of concurrent connections a LB can support, and further addslatency to request-reply transactions.

Still with reference to FIG. 6, when the network uses IPv6 and atransaction is based on IPv6 exchanges as described herein, the originalclient's IPv6 address will remain persistent and made available in theLBSPO header. The LB can use the application client's IPv6 address asstored in the LBSPO header along with other load balancing criteria forinitial server selection upon receipt of the first TCP SYNC packet. TheLB can use responding server's IPv6 address (included in the firstserver response with a LBSPO header) and the client's IPv6 address formaintaining session persistence. The intermediate proxy servers will andshould transparently pass the LBSPO header of each application clientrequest and will and should also transparently pass the associatedresponse from LBs or directly from servers (in Direct Server Return(DSR) scenarios). By using the LBSPO header with IPv6 data packets, theLB does not have to use delayed binding, and can therefore avoid costlysequence number translation that otherwise must be performed.

With reference to FIG. 11, and with further reference to FIGS. 7-10, amethod for performing load balancing and session persistence ispresented below. This illustrative method is based on the use of theIPv6 session persistence option in a destination extension header (LBSPOheader), by both the client and the server, as well as allintermediaries (unless a forward compatibility option from IPv4 to IPv6is in place). On the client side, the client application inserts its ownIPv6 address in the client field 511 of the LBSPO header and leavesserver field 513 all zeroes. The client application, upon receiving afirst response from the server, caches the responding server's IPv6address for all subsequent IPv6 packets exchanged during the samesession. In subsequent exchanges with the server, the client applicationinserts in the LBSPO header both the client's and responding server'sIPv6 address in fields 511, 513, respectively.

On the server side, when a server receives a first packet for a newsession, the server caches the sending client address from the sessionpersistence option for insertion in subsequent packets exchanged withthat client. In the first packet response to the client, the serverinserts its IPv6 address in the server field 513 of the LBSPO header,and also fills in the client field 511 with the client's IPv6 address.For all subsequent exchanges with the client, all the IPv6 packetsinclude the LBSPO header with both the client's and the server's IPv6addresses. The server may also check whether its own IPv6 address is thesame as the data in the server field 513 of incoming IPv6 packets' LBSPOheader.

Initially, in step 1101, a particular client 601 initiatescommunications with a desired device, application or service based on aknown virtual IP address by sending data packet 701. Data packet 701includes a sender address identifying the particular client 601, adestination address identifying the desired service or application (inthis example, using a virtual IP address). Data packet 701 also includesin the “Next Header” field a value of 60, indicating that a destinationsoptions extension header is included. The destination options extensionheader identifies a header length of 34, option 1 (LBSPO header), andpayload length 4 (indicating 32 bytes). The payload stores a persistentclient address based on the client 601, and further stores all zeros asa persistent server address because the server that will ultimatelyhandle the client's communications is not yet known for sessionpersistence and load balancing purposes.

In step 1103 the data packet is received and processed by a proxyserver. In step 1105 the proxy server forwards data packet 703, e.g.,out into a wide area network for ultimate delivery to the destinationaddress. As shown in packet 703, the proxy server has altered the senderaddress in the IPv6 header to be that of the proxy server, but leavesthe destination address and the LBSPO header unchanged. Any proxy serverhandling data packets in accordance with this method should preferablytransparently pass the LBSPO header included in client-originatedmessages and associated responses (either from LBs or directly fromservers in Direct Server Return (DSR) scenarios) without change oralteration.

In step 1107 message 703 is received and processed by a LB, whichselects a particular server (e.g., server 631) to which the messageshould be sent. Any LB acting in accordance with this illustrativemethod shall read and process the LBSPO header for an IPv6 packet. Forthe first packet in the exchange (such as a TCP Sync packet), the IPv6address of the client 511 is used to select a server along with otherload balancing criteria. In all IPv6 packets forwarded to subtendingservers, the LB includes the LBSPO header. The LBSPO header in the firstpacket to the selected server will contain only on application client'sIPv6 address, and not the server IP address. The LBSPO header in allsubsequent packets will have the IPv6 address of both the client 601 andthe responding server 631. The LB also includes the LBSPO header in eachresponse back to a proxy server or client 601, and the contents of theLBSPO header should be the same as that from the responding server 631.For all subsequent packets from client 601 for the same session, the LBpreferably sends the packets to the previous responding server 631 whoseIPv6 address is indicated in server field 513 of the LBSPO header.

In step 1109 the LB sends message 705 to server 631. As shown in message705, the LB has altered the sender address to be the virtual IP (VIP)address of the LB, and has altered the destination address to be that ofthe selected server 631, while leaving the LBSPO header unchanged.According to one alternative, the LB might insert the address of theselected server into server field 513, rather than merely forwarding thepacket and letting the server insert its own address. However, when LBperformed actions are being minimized in order to maximize the number ofconcurrent connections that a LB can process, this action can bedeferred by the LB and performed by the selected server.

In step 1111 server 631 receives and processes message 705 and preparesan appropriate response. In step 1113 server 631 sends its first replymessage 801. As shown in message 801, server 631 sends the message tothe LB VIP address, indicating its own address as the sender of themessage. In addition, server 631 has altered the LBSPO header toindicate the address of the server 631 as the server address 513, whileleaving the client address 511 unchanged.

In step 1115 the LB receives and processes message 801 and determines anext hop accordingly. In step 1117 the LB sends message 803. As shown inmessage 803, the LB changes the sender address to be the virtual IPaddress of the LB, and changes the destination address to be that of theproxy server (or proxy VIP) from which message 703 was received. The LBleaves the LBSPO header unchanged (the LBSPO header will remainunchanged throughout the remainder of session communications betweenclient 601 and server 631).

In step 1119 the proxy server receives and processes message 803 anddetermines the next hop accordingly. In step 1121 the proxy server sendsmessage 805 to client 601. As shown in message 805, the proxy serverchanges the destination address to be that of the originally sendingclient 601, while leaving other address and LBSPO header informationunchanged.

In step 1122 client 601 receives and processes message 805. Afterprocessing message 805, in step 1123 client 601 sends a subsequentmessage 901 as part of the same session. As shown in message 901, client601 now includes both its own address and the address of the server 631in the LBSPO header, which remain unchanged from those included inpreviously received message 805 and will remain unchanged for theduration of the session between client 601 and server 631. In step 1125the proxy server receives and processes message 901. In step 1127 theproxy server sends message 903 after having changed the sender addressaccordingly. Information in the LBSPO header remains unchanged.

In step 1129 the LB receives and processes message 903. In step 1131 theLB sends message 905 to server 631 after having changed the sender anddestination addresses accordingly. Information in the LBSPO headerremains unchanged. In step 1133 server 631 receives and processesmessage 905 and performs whatever action is requested by client 601.

In step 1135 server 631 sends message 1001 (for example, a responsemessage based on message 905). Server 631 initially sets the senderaddress as that of server 631, sets the destination to be that of theLB's VIP address, and leaves information in the LBSPO header unchangedbased on message 905. In step 1137 the LB receives and processes message1001. In step 1139 the LB sends message 1003 after having changed thesender and destination addresses accordingly. Information in the LBSPOheader remains unchanged.

In step 1141 the proxy server receives and processes message 1003. Instep 1143 the proxy server sends message 1005 after having changed thedestination address. Information in the LBSPO header remains unchanged.In step 1145 client 601 receives and processes message 1005. If, asdetermined in step 1147, further communications between client 601 andserver 631 are needed, e.g., the session is ongoing, then the methodreturns to step 1123 where the client 601 sends another message toserver 631. Otherwise, the method may terminate.

The method may be altered from that described above while maintainingsame or similar functionality. Multiple steps may be combined,reordered, or split into lower levels of granularity, without alteringthe load balancing and session persistence capabilities describedherein. For example, step 1147 may be skipped after step 1122(proceeding directly to step 1123), based on the assumption that atleast one subsequent set of messages will be required after the initialsession is established. Other alternatives may also be possible.

According to one alternative, the payload 407 of one or more LBSPOheaders may be encrypted such that only authorized nodes (e.g., client,server, approved intermediaries) can decrypt the LBSPO header toidentify the client and server addresses included therein. By encryptingthe LBSPO header payload, packing sniffing software and/or other malwaremay be prevented from detecting an endpoint IP address which could beused in a nefarious attempt to benefit from intercepted communications.

With reference to FIG. 12, a load balancing node may maintain sessionpersistence while performing load balancing based on the methods andsystems described above. FIG. 12 illustrates a sample session tablemaintained by a LB, e.g., by LB 620, during administration of 6 incomingpackets. Server selection is based on existing load balancing techniquesand/or algorithms when no server information is present in a LBSPOheader. When server information is present in a LBSPO header, a serveris selected based on the included server information. The information inFIG. 12 is based on traffic having gone through an ISP or enterpriseproxy server before reaching the LB (as evidenced by the Source beingProxyl for each connection). However, that need not be the case. Inaddition, FIG. 12 does not include second packets sent from clients thatacknowledge the TCP-Sync response from a server during the TCP 3-wayhandshake process.

As shown in FIG. 12, a first packet is received from Proxyl identifyinga destination of VIP1 with no port ID (e.g., a TCP Sync packet), andincluding a LBSPO header with client=C1 (e.g., client 601) and server=0.Based on no server indicated, the LB assigns a server based on its loadbalancing algorithm(s) otherwise in place, and sends packet 1 to SERV1(e.g., client 631). The LB later receives a second packet from Proxylidentifying a destination of VIP1 on port 80 (HTTP), and including aLBSPO header with client=C1 and server=SERV1. Based on the LBSPO header,the LB sends the message to SERV1.

The LB next receives a third packet from Proxyl identifying adestination of VIP1 on port 21 (FTP), including a LBSPO header withclient=C1 and server=0. Even though client C1 has previouslycommunicated with a server managed by the LB, the LBSPO header indicatesserver=0. This may occur, for example, where a server does not returnits address information in the server field of a LBSPO header. Based onno server being indicated in the LBSPO header, the LB selects a serverbased on its load balancing algorithm(s), and forwards the packet toSERV2 (e.g., server 632).

The LB later receives a fourth packet from Proxyl identifying adestination of VIP1 on port 443 (HTTPS). The fourth packet may be aresult of a user entering a secure mode, e.g., a user selecting a securecheckout feature on a website, and thereby switching from HTTP to HTTPS.The fourth packet includes a LBSPO header with client=C1 andserver=SERV1. Based on the LBSPO header, the LB forwards the message toSERV1.

The LB receives a fifth packet from Proxyl identifying a destination ofVIP2 with no port ID (e.g., a TCP Sync packet), but including a LBSPOheader having client=C2 (e.g., client 602) and server=0. Based on noserver being indicated in the LBSPO header, the LB selects a serverbased on its load balancing algorithm(s), and sends the packet to SERV3(e.g., server 633). When the LB subsequently receives a sixth packetfrom Proxyl identifying a destination of VIP2 on port 80 (HTTP), andhaving a LBSPO header identifying client=C2 and server=SERV3, the LBforwards the message to SERV3.

The LB may or may not perform any security checks when packets arereceived specifying a certain server. For example, one or more maliciousnodes and/or users might attempt a denial-of-service (DoS) type attackby flooding a particular server with data packets. In doing so, themalicious group might include the server address in the server field 513of the LBSPO header. However, because each LB typically performs loadbalancing for up to 20 servers or more, even if the DoS attack on asingle server were successful, the remaining servers would beunaffected. The owner of the LB therefore is not typically concernedwith a DoS attack on a single end server. A bigger problem is a denialof service attack on the VIP address of the service, in which case theLB would respond to such an attack as it would prior to implementationof the LBSPO header.

The LBSPO header may be used in large-scale deployments on IPv6networks, e.g., in large data centers that server as a foundation ofinformation-driven businesses. By using a LBSPO header with IPv6 enabledclient devices, IPv6 enabled servers and IPv6 enabled load balancers, adata center can more efficiently administer connections with a largerbase of users.

The above description is not meant to be limiting the implementation ofsession persistence information in a destination options extensionheader. Rather, the above is illustrative only. Other alternativeimplementations may be used. For example, according to one alternative,the order of the client and server fields in a LBSPO header could bereversed. Other information may be included in the session persistencepayload in addition to or in place of the client and server addresses.In one example, instead of client and server addresses, random numbersmay be used to preserve secrecy of client and/or server addresses. Therandom numbers may be specified to be of a length or complexity suchthat the probability of two machines generating the same random numberis minimized. Sessions could then be maintained by matching the randomnumber generated by a client application with the random numbergenerated by the assigned server for that session. The randomness of thenumber is unique enough so that load balancers in an IPv6 enablednetwork can perform load balancing upon the arrival of a first packetfrom a proxy server in its data path. However, the server preferablyuses its IPv6 address, instead of random number, for the 2nd field ofthe LBSPO, because the use of a random number in the server field wouldmake it difficult for the load balancer to identify the server without apriori arrangement, and such an a priori arrangement is preferablyavoided to simplify the operations that must be performed by the loadbalancer.

In other alternatives, usernames or other unique ID of a user, and/or anencrypted signed data field (such as a hash), could be used instead ofIPv6 addresses, and the length of the LBSPO header payload could bealtered accordingly. The encrypted signed data field may be inserted bya client to prove to a server (or LB) that the client is the same clientas that which the server is already communicating in another session.Other alternatives may also be used.

One or more aspects may be embodied in computer-usable or readable dataand/or computer-executable instructions, such as in one or more programmodules, executed by one or more computers or other devices as describedherein. Generally, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types when executed by a processor ina computer or other device. The modules may be written in a source codeprogramming language that is subsequently compiled for execution, or maybe written in a scripting language such as (but not limited to) HTML orXML. The computer executable instructions may be stored on a tangiblecomputer readable medium such as a hard disk, optical disk, removablestorage media, solid state memory, RAM, etc. As will be appreciated byone of skill in the art, the functionality of the program modules may becombined or distributed as desired in various embodiments. In addition,the functionality may be embodied in whole or in part in firmware orhardware equivalents such as integrated circuits, field programmablegate arrays (FPGA), and the like. Particular data structures may be usedto more effectively implement one or more aspects described herein, andsuch data structures are contemplated within the scope of computerexecutable instructions and computer-usable data described herein.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A non-transitory computer readable medium having a data structure stored thereon, said data structure comprising: an IP header; a destination options extension header (DOEH) comprising: a first data field identifying the DOEH as conforming to a predefined option usable for load balancing and session persistence, a second data field identifying a length of a DOEH payload field, the DOEH payload field comprising third and fourth data fields, wherein the third data field stores a client identifier, and the fourth data field stores a server identifier; and an IP payload.
 2. The computer readable medium of claim 1, wherein the client identifier is an address of a client, and wherein the server identifier is an address of a server assigned to a session with the client.
 3. The computer readable medium of claim 2, wherein the first data field is 8 bits storing a binary value of 1, wherein the second data field is 8 bits storing a binary value of 4, wherein the third data field is 128 bits storing the IPv6 address of the client, and wherein the fourth data field is 128 bits storing the IPv6 address of the server.
 4. The computer readable medium of claim 1, wherein a value of the third data field, once established by a client, remains fixed within a same session, and wherein a value of the fourth data field, once established by a server, remains fixed within the same session.
 5. An apparatus, comprising: a processor, and memory storing computer executable instructions that, when executed by the processor, cause the apparatus to perform: receiving an Internet Protocol (IP) data packet comprising: an IP header; a destination options extension header (DOEH) comprising: a first data field identifying the DOEH as conforming to a predefined option usable with load balancing, a second data field identifying a length of a DOEH payload field, the DOEH payload field comprising third and fourth data fields, wherein the third data field stores a client identifier, and the fourth data field stores a server identifier; and an IP payload; and processing the IP data packet based on the IP header without allowing modification to the DOEH header.
 6. The apparatus of claim 5, wherein the client identifier is an address of a client, and wherein the server identifier is an address of a server assigned to a session with the client.
 7. The apparatus of claim 6, wherein the first data field is 8 bits storing a binary value of 1, wherein the second data field is 8 bits storing a binary value of 4, wherein the third data field is 128 bits storing an IPv6 address of the client, and wherein the fourth data field is 128 bits storing an IPv6 address of the server.
 8. The apparatus of claim 5, wherein a value of the third data field, once established by a client, remains fixed during a same session with the server, and wherein a value of the fourth data field, once established by a server, remains fixed during the session.
 9. The apparatus of claim 5, wherein processing the IP data packet comprises forwarding the data packet to a next hop in a data network.
 10. The apparatus of claim 5, wherein processing the IP data packet comprises selecting a server from a group of available servers based on the DOEH payload field.
 11. The apparatus of claim 10, wherein selecting the server comprises: when server information is present in the fourth data field, selecting the server identified in the fourth data field; and when no server information is present in the fourth data field, selecting the server based on a load balancing algorithm and the client identifier.
 12. The apparatus of claim 5, wherein processing the data packet comprises associating an HTTPS packet with a previously received HTTP packet based on the DOEH.
 13. A method comprising: receiving at an intermediary node of an Internet Protocol (IP) data network an IP data packet comprising: an IP header; a destination options extension header (DOEH) comprising: a first data field identifying the DOEH as conforming to a predefined option usable with load balancing, a second data field identifying a length of a DOEH payload field, the DOEH payload field comprising third and fourth data fields, wherein the third data field stores a client identifier, and the fourth data field stores a server identifier; and an IP payload; and processing the IP data packet at the intermediary node based on the IP header without allowing modification to the DOEH; and sending the IP data packet by the intermediary node to either of a next hop node or a destination server, based on the processing of the data packet.
 14. The method of claim 13, wherein the client identifier is an address of the client, and wherein the server identifier is an address of a server assigned to a session with the client.
 15. The method of claim 13, wherein the first data field is 8 bits storing a binary value of 1, wherein the second data field is 8 bits storing a binary value of 4, wherein the third data field is 128 bits storing an IPv6 address of the client, and wherein the fourth data field is 128 bits storing an IPv6 address of the server.
 16. The method of claim 13, wherein a value of the third data field, once established by a client, remains fixed during a same session, and wherein a value of the fourth data field, once established by a server, remains fixed during the same session.
 17. The method of claim 13, wherein the intermediary node is a router, and the sending is sending the IP data packet to the next hop node.
 18. The method of claim 13, wherein the intermediary node is a load balancer, and processing the IP data packet comprises selecting a destination server from a group of available servers, based on the DOEH payload field.
 19. The method of claim 18, wherein selecting the destination server comprises: when server information is present in the fourth data field, selecting the destination server identified in the fourth data field; and when no server information is present in the fourth data field, selecting the destination server based on a load balancing algorithm.
 20. The method of claim 18, wherein the IP data packet is an HTTPS packet, and wherein processing the data packet comprises associating the IP data packet with a previously received HTTP IP data packet, based on the destination options extension header.
 21. One or more computer readable storage media comprising computer executable instructions that, when executed by a device, configure the device to perform: receiving an Internet Protocol (IP) data packet, said IP data packet comprising: an IP header; a destination options extension header (DOEH) comprising: a first data field identifying the DOEH as conforming to a predefined option usable with load balancing, a second data field identifying a length of a DOEH payload field, the DOEH payload field comprising third and fourth data fields, wherein the third data field stores a client identifier, and the fourth data field stores a server identifier; and an IP payload; and processing the IP data packet based on the IP header without allowing modification to the DOEH header.
 22. The computer readable storage media of claim 21, wherein the client identifier is an address of a client, and wherein the server identifier is an address of a server assigned to a session with the client.
 23. The computer readable storage media of claim 22, wherein the first data field is 8 bits storing a binary value of 1, wherein the second data field is 8 bits storing a binary value of 4, wherein the third data field is 128 bits storing an IPv6 address of the client, and wherein the fourth data field is 128 bits storing an IPv6 address of the server.
 24. The computer readable storage media of claim 21, wherein a value of the third data field, once established by a client, remains fixed during a same session with the server, and wherein a value of the fourth data field, once established by a server, remains fixed during the session.
 25. The computer readable storage media of claim 21, wherein processing the IP data packet comprises forwarding the data packet to a next hop in a data network.
 26. The computer readable storage media of claim 21, wherein processing the IP data packet comprises selecting a server from a group of available servers based on the DOEH payload field.
 27. The computer readable storage media of claim 26, wherein selecting the server comprises: when server information is present in the fourth data field, selecting the server identified in the fourth data field; and when no server information is present in the fourth data field, selecting the server based on a load balancing algorithm and the client identifier.
 28. The computer readable storage media of claim 21, wherein processing the data packet comprises associating an HTTPS packet with a previously received HTTP packet based on the DOEH. 